In a semiconductor package assembly process, a method in which an aluminum electrode and an inner lead of a semiconductor chip are electrically connected by means of a gold wire by thermo-compression bonding is currently a mainstream. In recent years, with the market trends of reduction in size, lightness and high performance of electronic devices, higher integration and high pin count of electronic components are in progress year by year. Thus, a wire bonding process which is more complex than before has been demanded, and when a copper lead frame is used, oxidation of a copper surface has become more advanced by exposing to high temperature of 200 to 250 degrees centigrade over a long period of time.
Under the circumstances described above, even in a semiconductor encapsulating material excellent in adhesion to a conventional unoxidized copper surface, adhesion to copper oxide having a different surface state is inferior in many cases, so that there has been a problem of detachment during mold releasing after encapsulating with a resin or during solder reflow.
Adhesion between an inserted article and an encapsulating material resin for inhibiting detachment is an index contrary to mold releasability with respect to a mold. Thus, there has been a problem such that when adhesion is improved, mold releasability is deteriorated and molding property is lowered. With higher integration of electronic components, in order to achieve both adhesion and mold releasability, addition of a polyethylene oxide wax and a half esterified product of a copolymer of α-olefin and a maleic acid as a mold releasing agent has been proposed before oxidation of a copper frame becomes a problem (for example, see Patent Documents 1 and 2). According to this method, there has been a problem of lowering adhesion of an encapsulating resin to an oxidized copper frame with the use of a polyethylene oxide wax together, even though adhesion to an unoxidized copper and mold releasability are excellent. Furthermore, there has been a problem of deteriorating continuous molding property (mold releasability such as air vent block or the like) in a copolymer consisting of a short α-olefin moiety having equal to or less than 25 carbon atoms as a mold releasing agent (for example, see Patent Document 3).